Let's talk now about policy ramifications and political reactions to today's court ruling. For that, we're joined by NPR national correspondent Mara Liasson. Hey there, Mara.

MARA LIASSON, BYLINE: Hi Audie.

CORNISH: So we have, in effect, a split decision. Two appeals courts ruling in different ways. What's the political spin so far?

LIASSON: Well, both sides are claiming victory, not surprisingly. The White House says it's extremely confident that when the Supreme Court finally resolves this issue, they will prevail. They're pointing to the Fourth Circuit decision. They're saying you don't need a fancy legal theory to know that Congress intended every eligible American to have access to the subsidies, not just ones that live in the 16 states that set up their own exchanges. But conservatives say the D.C. Circuit Court ruling kneecaps Obamacare, and that if the Supreme Court upholds it, Obamacare will start to unravel and that's probably true.

After the Supreme Court decision in 2012 that declared Obamacare itself constitutional, this clearly is the biggest legal threat. Only the Supreme Court we know now can undo Obamacare - Congress can't as long as there's a Democratic president.

CORNISH: One idea being thrown around, Mara, whether the split ruling - is it basically the outcome of a drafting error in the health care law?

LIASSON: Well, drafting errors do happen and you used to be able to correct them by going to Congress. But because we live in a completely dysfunctional polarized political universe, it's impossible for the administration - almost impossible for the administration to go to Congress to get a technical correction made to the ACA because Congress - at least the House of Representatives - doesn't want to correct Obamacare, it wants to repeal Obamacare. And so that's how differences of opinion like this end up in the Supreme Court. However, if the D.C. Circuit Court were eventually upheld, we should just say that many millions of people - 5 million now, 7.3 million projected by 2016 - could eventually lose subsidies because the mandate would apply to fewer people.

CORNISH: Mara, such high stakes here listening to you rattle off those numbers of who's affected. Give us a sense of the political ramifications, especially since we are, of course, in an election year.

LIASSON: Well, we're entering the third straight election where Obamacare itself is an issue. It's still animating conservatives, but for a while, Democrats had felt some of its sting had been dampened. Since the rollout problems had been fixed, Obamacare seemed to recede a little bit, but here we are four months before an election talking about another existential legal challenge to Obamacare.

It is possible this ruling could revive the whole war about health care before the November elections, but I think the real big political impact comes in 2016 because by then, the Supreme Court will have resolved this issue. Then there could be huge political effects - either, as conservatives argue, people will be so happy to see this unpopular law gutted, they'll be liberated from the Obamacare mandate and they'll reward Republicans, or as Affordable Care Act supporters predict, there could be a huge backlash. They say it's one thing to strike down something that hasn't yet gone into effect, quite another to take something away from people who've come to rely it.

CORNISH: And briefly Mara, is there a sense that the legal effort to sort of undo Obamacare, as they call it, has worked much better than the political effort?

LIASSON: Well, it certainly has because it still has a lease on life with this ruling. The political effort is stymied. The House can vote a hundred times to repeal Obamacare, but it won't go anywhere as long as there's a Democrat in the White House.